Evaporator including radiant heater defrost means



Oct. 25, 1966 R- G. TURNER EVAPORATOR INCLUDING RADIANT HEATER DEFROST MEANS Filed May 12, 1965 23 j Z2 54 2| l 5 8) L ,el 40 n i Vi: \J mins 1 uuuwr 39 27 L 1 3s H26 l 28 I 550 INVENTOR.

ROBERT CI- TURNER ms ATT RNEY United States Patent EVAPORATGR INCLUDING RADIANT HEATER The present invention relates to household refrigerators and is more particularly concerned with an improved refrigerant evaporator structure including a radiant heater for periodically defrosting of the evaporator.

Many modern domestic refrigerators include an evaporator which normally operates at frost collecting temperatures substantially below freezing in order to maintain a freezer compartment at below freezing temperatures. In order to prevent this layer of frost from materially affecting the eliiciency of the evaporator, it is necessary to provide means for periodically heating the evaporator to melt the frost thereon.

One object of the present invention is to provide a defrostable evaporator structure including a fin-on-tube evaporator and a radiant heater defrost means for warming the evaporator to defrost temperatures.

Another object of the invention is to provide a fin-on tube evaporator and improved means for mounting a radiant heat defroster thereon.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with the illustrated embodiment of the present invention there is provided a refrigerant evapora tor including a plurality of parallel refrigerant conduits and a fin structure comprising a plurailty of plate-like fins extending transversely of the conduits. Slots in each of the fins form a channel in the fin structure paralleling the refrigerant conduits. The defrost heater component comprises a quartz tube, a radiant heater coil in the tube and end caps on each end of the tube, the end caps being designed to support the heater in the channel with the tube out of contact with the fins. The caps also include air or breather passages communicating with the interior of the tube so designed as to prevent the migration of defrost water or moisture into the tube.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

FIGURE 1 is a vertical side sectional view of a portion of a household refrigerator embodying the present invention;

FIGURE '2 is a sectional view taken generally along line 2-2 of FIGURE 1.

With reference to the drawing, there is shown a refrigerator comprising insulated walls defining an upper freezer compartment I intended to operate at a temperature below freezing and a lower fresh food compartment 2 adapted to operate at an above freezing temperature of about 35 to 40 F. The two compartments are separated by a horizontal insulating partition 3. The access opening to the freezer compartment 1 is closed by means of an insulating door 4 while the access opening to the fresh food compartment 2 is closed by means of an insulating door 5. In the illustrated embodiment of the invention, a single evaporator 7 for refrigerating the air supplied to the two compartments 1 and 2 is contained within an evaporator chamber 8 formed within the insulated partition 3. It is to be understood that the refrigerator also includes a refrigerant condensing unit for supplying condensed refrigerant to the evaporator 7 and for withdrawing vaporized refrigerant therefrom.

For the purpose of maintaining the two storage compartments 1 and 2 at their desired operating temperatures, air streams from these two compartments are passed over the evaporator 7 and refrigerated or cooled air streams from the evaporator are returned to the compartments by means of a single fan generally indicated by the numeral 10. More specifically, the air is withdrawn from the freezer compartment 1 through a passage 11 connecting the freezing compartment with one end of the chamber 8 and a major portion of the air cooled or refrigerated by the evaporator 7 is returned to the freezer compartment through an air passage 12 adjacent the outlet from the fan 10. The air leaving the passage 12 flows into the rear end of a tunnel 14 provided in the bottom of the freezer compartment 1 for the storage of one or more freezing trays 15 and passes from the tunnel into the freezer compartment through a plurality of passages including louvered passages 16.

Air from the fresh food compartment 2 is drawn into the evaporator chamber 8 through a plurality of spaced passages 18 adjacent to the front of the partition 3. This fresh food air becomes mixed with the air flowin g from the freezer compartment 1 and the air mixture passes over the evaporator 7. A relatively smaller amount of the cooled or refrigerated air flowing from the rear or outlet end of the chamber 8 is circulated by the fan 10 downwardly through the outlet passage 19 into the fresh food compartment 2.

The evaporator 7, as is more clearly shown in FIGURE 2 of the drawing, comprises a plurality of parallel refrigerant passes 21 series connected by means of return bends 22 and a fin structure comprising a plurality of parallel plate-type fins 23 threaded onto the passes 21 and extending transversely thereto. During cooling operation of the refrigerator, air from the two compartments 1 and 2 is drawn through this fin structure in a direction generally parallel to the fins 23, that is, between the fins. As the refrigerant circulating through the passes 21 maintains these passes and the fins 23 at temperatures below freezing, a layer of frost gradually accumulates on some or all of the surfaces of the evaporator structure.

For the purpose of periodically Warming the evaporator surfaces to defrosting temperatures, there is provided heating means in the form of a radiant heater 25 extending transversely of the fin structure and centrally positioned within that structure. This heater comprises a tubular member 26 of quartz or similar glass-like insulating material having good thermal shock and radiant heat transmitting properties and a helical radiant heater coil 27 within the tubular member 26. A preferred material is that known as Vycor. Sealing caps 28 provided on each end of the tubular member 26 provide means for housing the electrical means connecting the coil 27 to a source of power and for sealing the ends of the tubular member to prevent moisture from entering the tubular member.

More specifically, each of the end caps 28 comprise a body of insulating material 29 such as a molded phenolic resin material. Each of the caps includes a vertical passage 3'0 and a horizontal passage 31 communicating with the vertical passage 30 intermediate the ends thereof. The end of the horizontal passage 31 is designed to fit over an end of the tubular member 26 and to be resi1i ently supported thereon by means of a sealing gasket 32 composed of silicone rubber or other highly heat resistant material. The gasket or seal 32 provides a shock mount for the tubular member 26 and reduces possible current leakage by preventing moisture from entering the tubular member or the cap through the joint area.

A terminal 35 for connecting one end of the heater coil 27 to a source of power is also provided in each of the caps 28. The terminals are generally contained within the horizontal passage 31 and each one has one end 36 suitably secured, as by resistance welding, to an S-looped configuration at the end of the heater coil 27 while the other end includes an anchoring hook 37 for contacting a portion of the inner wall of the vertical passage 3% and anchoring the terminal 35 within the cap. The terminals 35 are preferably composed of a sheet stainless steel having a low thermal conductivity in order to minimize heat transfer from the coil 27 to the interior of the cap and are also formed to include a slot portion 39 opening upwardly towards the upper end 40 of the passage 30 for receiving a connector blade or terminal 41 for connecting an electrical lead 42 to the terminal member 35. A sleeve 44 enclosing the terminal end of the lead 42 and adapted to slip over the portion of the cap defining the upper end 40 of the vertical passage prevents moisture from entering the upper end of the cap around the lead 42.

The entire heater assembly is supported by the caps within a channel 47 defined by vertical slots in each of the fins in a position such that the tubular member 26 is held in spaced relationship with the adjacent fin areas by means of the caps 28. Each of the caps is provided with an annular groove 48 in the portion thereof surrounding or enclosing one end of the tubular member 26, which slots receive the opposed vertical side edges of a slot 47 in each end fin 23 so that in addition to positioning the tubular member 26 in spaced relationship with the vertical side walls of the slot 47 the tubular member 26 is also maintained in spaced relationship with the bottom portions 50 of these slots. 7

A reflector 51 positioned in the channel in spaced relationship with the tubular member 26 prevents substantial radiation of heat from the coil 27 in an upward direction. This reflector 51 in the form of an inverted channel member includes vertical side edges 52 adapted to engage and be supported on shoulders 53 formed in the vertical side edges of the slots 47 so as to maintain the reflector 51 spaced above the tubular member 26.

Both the defrost heater, or more specifically the end caps thereof, and the reflector 51 are secured in position by means of hold down clips 54, each comprising a return bend portion 55 for clamping an upper edge of an end fin 23, a first arm 57 for engaging the cap 28, and a second arm 58 having an end section 59 spaced from the remaining portion of the clip and overlying an end of the reflector 51.

During operation of the defrost means or in other words when a current is passed through the coil 27,the reflector 51 is quickly heated and in order to prevent the hot reflector from adversely effecting the end caps 28, the opposite ends of the reflector 51 are spaced from the caps. Also in order to prevent convection currents of hot air from flowing along the reflector from the ends thereof towards the end caps 28, the upper surface of the channel adjacent each end thereof is provided with at least one vent opening 61 defined by lancing a tab 62 from the top surface of the reflector in a direction toward the end of the reflector so that convection currents are directed upwardly through the openings 61 and prevented by the tab 62 from flowing in the direction of the caps 28.

Since the interior of the tubular member 26 is subjected to temperature changes from below freezing temperatures during operation of the evaporator for cooling the refrigerator compartments to temperatures in the neighborhood of 500 to 700 F. during defrost operation of the heater, it is desirable also that means be provided for venting the tube. This is accomplished by a breather passage comprising the lower portion of the vertical passage 30 which communicates with the horizontal passage 31 that in turn communicates with the interior of the tube 26 and since the exposed or open end of this passage opens downwardly. moisture cannot enter the tube 26.

While there has been shown and described a particular embodiment of the present invention it is to be understood that it is not limited thereto and it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination,

a refrigerant evaporator,

a radiant defrost heater comprising a transparent, heat resistant tube open at both ends, end caps resiliently mounted on each end of said tube, and a radiant heater coil in said tube,

each of said caps comprising a body of insulating material supporting said defrost heater in heating arrangement with said evaporator and to maintain said tube in spaced relation with said evaporator,

each of said caps including a vertical passage and a horizontal passage connected to said vertical passage and resiliently mounted on an end of said tube,

the lower end of said vertical passage and said horizontal passage forming an air passage connected to the interior of said tube,

a terminal in said horizontal passage including one portion extending into said tube and secured to one end of said heater coil and a second portion positioned in said vertical passage and means for connecting a lead to said second portion of said terminal.

2. In combination,

a refrigerant evaporator including a plurality of refrigerant conduits and a fin structure comprising a plurality of parallel plate-like fins,

a slot in each of said fins forming a channel in said fin structure parallel to and having a bottom portion centrally positioned relative to said conduits,

a defrost heater comprising a quartz tube open at both ends, end caps resiliently mounted on each end of said tube, and a radiant heater coil in said tube,

each of said caps comprising a body of insulating material supported in the slot in one of said fins to maintain said tube in spaced relation with the walls of said fins,

resilient clips for securing said caps within said channel, each of said clips comprising a return bend portion anchoring said clip on an upper portion of said one of said fins and an arm engaging one of said caps,

each of said caps including a horizontal air passage having one end connected to the interior of said tube and the other end opening into a bottom surface of said cap, 7

a terminal in said horizontal passage including one portion extending into said tube and secured to one end of said heater coil and a second portion positioned in said passage, and means for electrically connecting a lead to said terminal.

3. In combination,

a refrigerant evaporator including a plurality of refrigerant conduits and a fin structure comprising a plurality of parallel plate-like fins,

a slot in each of said fins forming a channel in said fin structure having a bottom portion centrally positioned in said fin structure,

a defrost heater comprising a tube of transparent electrically insulating heat transmitting material open at both ends, end caps resiliently mounted on each end of said tube, and a radiant heater coil in said tube,

each of said caps comprising a body of insulating material supported in the slot in one of said fins to maintain said tube in spaced relation with the walls of said fins,

a reflector in said channel above and in spaced relation with said tube and said end caps, said reflector including a top section and depending side flanges,

means for securing said caps and reflector within said channel,

said reflector including at least one opening in the top section thereof adjacent each end thereof and a tab extending downwardly therefrom between said opening and the cap adjacent thereto to deflect convection currents from said radiant heater away from said caps,

each of said caps including a vertical passage and a horizontal passage connected to said vertical passage and resiliently mounted on an end of said tube,

the lower end of said vertical passage and said hori' zontal passage forming an air passage connected to the interior of said tube,

a terminal in said horizontal passage including one portion extending into said tube and secured to one end of said heater coil,

an electrical lead extending into the upper end of said vertical passage and including disconnect means for electrically connecting said lead to said terminal.

4. In combination,

a refrigerant evaporator including a plurality of parallel refrigerant conduits and a fin structure comprising a plurality of transverse plate-like fins,

a slot in each of said fins forming a channel in said fin structure parallel to and having a bottom portion centrally positioned relative to said conduits,

a defrost heater comprising a quartz tube open at both ends, end caps resiliently mounted on each end of said tube, and a radiant heater coil in said tube,

each of said caps comprising a body of insulating material supported in the slot in one of said fins to maintain said tube in spaced relation with the walls of said fins,

a reflector in said channel above and in spaced rela tion with said tube and said end caps, said reflector including a top section and depending side flanges,

resilient clips for securing said caps and reflector within said channel, each of said clips comprising a return bend portion anchoring said clip on an upper portion of said one of said fins, a first arm engaging one of said caps and a second arm having an end section spaced from said first arm and overlying an end of said reflector,

said reflector including at least one opening in the top section thereof adjacent each end thereof and a tab extending downwardly therefrom between said opening and the cap adjacent thereto to deflect convection currents from said radiant heater away from said cap,

each of said caps including a vertical passage and a horizontal passage connected to said vertical passage and enclosing an end of said tube,

the lower end of said vertical passage and said horizontal passage forming an air passage connected to the interior of said tube,

a terminal in said horizontal passage including one portion extending into said tube and secured to one end of said heater coil and a second portion positioned in said vertical passage,

an electrical lead extending into the upper end of said vertical passage and including disconnect means for electrically connecting said lead to said second portion of said terminal and a sealing cap on said conductor for closing the upper end of said vertical passage.

References Cited by the Examiner UNITED STATES PATENTS 2,211,605 8/1940 Moehler 313318 X 3,089,972 5/1963 Larson et al 313-318 X 3,099,914 8/1963 De Witt et a1. 62-276 References Cited by the Applicant UNITED STATES PATENTS 2,126,285 8/1938 Schaaf.

ROBERT A. OLEARY, Primary Examiner.

N. R. WILSON, Assistant Examiner. 

1. IN COMBINATION, A REFRIGERANT EVAPORATOR, A RADIANT DEFROST HEATER COMPRISING A TRANSPARENT, HEAT RESISTANT TUBE OPEN AT BOTH ENDS, END CAPS RESILIENTLY MOUNTED ON EACH END OF SAID TUBE, AND A RADIANT HEATER COIL IN SAID TUBE, EACH OF SAID CAPS COMPRISING A BODY OF INSULATING MATERIAL SUPPORTING SAID DEFROST HEATER IN HEATING ARRANGEMENT WITH SAID EVAPORATOR AND TO MAINTAIN SAID TUBE IN SPACED RELATION WITH SAID EVAPORATOR, EACH OF SAID CAPS INCLUDING A VERTICAL PASSAGE AND A HORIZONTAL PASSAGE CONNECTED TO SAID VERTICAL PASSAGE SAGE AND RESILIENTLY MOUNTED ON AN END OF SAID TUBE, THE LOWER END OF SAID VERTICAL PASSAGE AND SAID HORIZONTAL PASSAGE FORMING AN AIR PASSAGE CONNECTED TO THE INTERIOR OF SAID TUBE, A TERMINAL IN SAID HORIZONTAL PASSAGE INCLUDING ONE PORTION EXTENDING INTO SAID TUBE AND SECURED TO ONE END OF SAID HEATER COIL AND A SECOND PORTION POSITIONED IN SAID VERTICAL PASSAGE AND MEANS FOR CONNECTING A LEAD TO SAID SECOND PORTION OF SAID TERMINAL. 